Primus’ bassist and main personality Les Claypool is selling one of his two main instruments,
the final prototype of his Pachyderm four-string bass, in order to raise money for his two-year-old nephew Matthew’s cancer treatment. Matthew was diagnosed with a rare form of leukemia as an infant, and he is currently in the hospital undergoing bone marrow transplant therapy.

Claypool and Primus have been raising money for Matthew with special performances and merchandise, but Claypool says treatment has been so costly that “we are just pushing against a tide of debt that my brother will be dealing with for many years,” with certain injections costing as much as $80,000 each. The bass is currently up for public auction, and Claypool explains that it will be used as the model for all future Pachyderm basses, which are being crafted to Claypool’s exact specifications by luthier Dan Maloney.

Claypool calls the instrument “the most playable and ergonomically comfortable instrument I could think of” and says that he crossed different elements of his favorite basses over the years to create this particular model. The bidding is currently just over $10,000, head over to eBay to bid on this amazing instrument and collector’s item from one of today’s most iconic bassists—you’ll be helping out Matthew and his family significantly in the process.